In recent years, the pixel size of solid-state imaging devices, which are used in a digital cameras or the like, has decreased to a range of approximately 1 μm in size. As pixel size shrinks, maintaining and/or improving image quality becomes very important. Since the amount of signal received by a photodiode type of a light receiving unit is reduced when the pixel size is reduced, improving the Signal to Noise Ratio (SNR) performance of a solid-state imaging device is a very important.
Since there are sensitivity differences between the three R, G, and B color filters used in an image sensor, when imaging an image, there is a case in which, for example, an imaged image is not viewed as a white image, and so-called coloring occurs, even when an object is actually white. In order to correct the coloring phenomenon, a White Balance (WB) function is provided in an imaging device. In general, in the WB, it is possible to improve the white balance by eliminating the difference in sensitivity between the R, G and B filters, by digitalizing signals which are obtained from the respective three color filters, and multiplying the digital signals by a gain corresponding to a sensitivity ratio between the filters. However, these types of WB corrections commonly used in the prior art leads to problems, since the amount of noise also increases when multiplying the signal by the gain, and thus the SNR of the device deteriorates as a result. The deterioration of the SNR is created, since it is not possible to isolate the noise component which is included in the signal.
Therefore, there is a need for a solid-state imaging device, and method of forming the same, that is able to reliably and accurately account for the variations in image signal received due to the variations in the color filter sensitivity, and improve its overall SNR performance.